In recent years, an erasing device is introduced according to a demand for saving of resources. The erasing device applies heat or light to a recording medium on which an image is formed with an erasable developing agent and erases the developing agent to thereby erase the image. Therefore, the recording medium after the erasing can be reused.
However, the erasing device in the past applies heat or light to the entire recording medium. Therefore, energy is wastefully consumed and deterioration of the recording medium is accelerated.
As a measure against this problem, there is proposed a technique for reading a recording medium on which an image is formed by a scan unit, calculating, from read data, a position where the image is formed, heating, with a thermal head, a section where the image is formed and irradiating light on the section to erase the image (see, for example, JP-A-6-270431).
However, with this technique, since the light is irradiated on a wide section of the recording medium, energy is still wastefully consumed and deterioration of the recording medium is still fast.